A trial balance lists every ledger account with its debit or credit balance at a point in time. If the books are correct, the totals of the debit and credit columns match. It is a first check on the integrity of the ledger and the starting point for preparing the profit and loss statement and balance sheet.
A trial balance that does not tally signals a posting error to investigate before finalising accounts.
Preparing one is mechanical: take the closing balance of every ledger account, place debit balances in one column and credit balances in the other, and total both. Because each posting carried equal debits and credits, the columns must agree — asset and expense accounts typically sit on the debit side, liabilities, equity and income on the credit side. Software produces this on demand for any date, which makes it the fastest health check the books have.
A tallied trial balance is necessary, not sufficient. Four families of error leave it undisturbed: omission, where a transaction was never recorded; commission, where the right amount hit the wrong account; compensating errors that cancel each other; and errors of principle, such as a capital purchase booked as an expense. Equality proves the arithmetic of posting, not the judgement behind it — the judgement is tested by scrutiny and reconciliation.
When the columns disagree, old tricks narrow the hunt. A difference divisible by two may be a balance listed on the wrong side; one divisible by nine suggests transposed digits, ₹5,400 entered as ₹4,500. Check whether the difference equals a whole ledger balance that was skipped, then work back through recent postings. Anything unresolved at closing is parked in a suspense account — which should be emptied, not carried forward year after year.